In the Zibaldone the concept of “enthusiasm” is indissolubly linked to reflection upon literature, and in particular upon poetry.

Showing his thoughts to be quite out of synchrony with contemporary “romantic” conceptions (not by chance did he also write on this theme in his essay on poetry Discorso di un Italiano intorno alla poesia romantica, in which against Romanticism, which propounded a “contemporary”, “useful” and “sentimental” art, he exalted Classicism, which produced poetry close to nature and the illusions  of antiquity), Leopardi believed in particular that for poetic invention enthusiasm was not only not necessary, but could indeed reveal itself to be harmful:

When it is not profound we want to communicate it, when it is profound no [85-6] – it is linked to physical vigour [96-7, 115] – in as much as it is “abstract, vague, indefinite” it aids execution, not poetic invention (which instead needs the memory of enthusiasm) [257-9]; indeed, “the poet at the height of his enthusiasm of passions etc. is not a poet, that is to say he is not capable of writing poetry” [714] – “A man of strong and vivid imagination  ... at a point of extraordinary and passing corporal vigour, of enthusiasm, desperation, of most vivid pain or whatever passion ... discovers a multitude of truth that many centuries are not enough for pure and cold geometric reason to discover” [1975-8, 3269-71] – “enthusiasm, inspiration, essential to poetry, are not lasting things. Nor can they be kept up too long in he who reads” [4372].